How to map/project bone coordinates to camera coordinates sytem/view?
So, here it is, was very close to the solution after the last update to the question 

for f in frame_numbers:
            scene.frame_set( f )   
            for wco in Bones16_WCO:
                print("world Coords:", wco)
                cco = bpy_extras.object_utils.world_to_camera_view(scene, cam, wco)       
                x=(round(cco.x * render_size[0]))
                y=(render_size[1]-round(cco.y * render_size[1]))